The typographical corrections below were made to the article on the date noted. These changes have been incorporated in the article and the details are documented here.

21 September 1999:

In the first sentence of paragraph 4 of the Results section:

The three progressive retinal degenerations....

was corrected to:

The progression of three retinal degenerations....

In paragraph 4 of the Discussion section:

...layers of photoreceptor nuclei remain.

was corrected to:

...layers of photoreceptor cell bodies remain.

In Figure 2, Figure 3, Figure 4, and Figure 5, duplicate captions were removed. Additionally, the text linking to the high resolution images for these figures was clarified. The sentence:

For larger versions of an individual image, click on its link.

was corrected to:

For a larger version of an individual image, click on the appropriately named text link below.

In the Figure 4 caption for G, a space was inserted between the comma and the number "12".

In the Figure 5 caption for B-D, "Figures 5b-d" was changed to "B-D".